Technical Abstract:
Elevated levels of starch in sugarcane juice adversely affect the processing quality of raw and refined sugar. Despite reports of differences among cultivars for starch content, most research has focused on processing aids to minimize the negative processing effects of starch. Deploying cultivars low in starch content is a more efficient, cost-effective, long-term strategy. In this study, starch content among sugarcane germplasm accessions and an experimental commercial population were measured. The objectives were to characterize the germplasm, to identify low starch accessions for possible future use in breeding, and to estimate genetic variability and broad sense heritability for starch content. Three sets of experiments were conducted. Experiment I consisted of 52 S. spontaneum and one S. officnarum accessions. Experiment II consisted of 49 accessions including 5 S. spontaneum, 13 S. barberi, 11 S. robustum, 8 S. sinense, 9 S. officinarum and 1 each of Erianthus sp., Miscanthus sp. and S. bengalense. Experiment III consisted of 76 entries including 6 cultivars and 70 experimental clones of F1 and BC1 origin derived from crosses between S. spontaneum and cultivars. Except for Experiment III which was a three replicate trial, the other experiments were un-replicated. Experiments I and II revealed significant differences in starch levels among the Saccharum species, and significant differences among clones within species. Generally, the cultivated Saccharum species produced less starch than their wild relatives. Saccharum species could be grouped into high starch (S. bengalense, Erianthus and S. spontaneum), medium starch (S. barberi, S. sinense and S. robustum) and low starch (S. officinarum and Miscanthus). In Experiment III, starch content was lowest among cultivars and highest among F1s. Genetic variation was substantial among the experimental clones leading to high (89%) broad sense heritability estimates. The results suggest that parents low in starch content could be selected even from among high starch species such as S. spontaneum. Such parents would ultimately be useful for breeding low starch cultivars.